Lamp base



FIG. 1 is a side elevational view of the lamp base of my new design;

FIG. 2 is a top plan view of the lamp base of FIG. 1;

FIG. 3 is a perspective view of the lamp base of FIG. 1; and,

FIG. 4 is an elevation view taken from the left side of FIG. 1. 

I claim the ornamental design for lamp base, as shown. 